Pressure sensitive adhesive sheet

ABSTRACT

A pressure sensitive adhesive sheet is provided which comprises a base material having insulation properties, an inorganic filler-containing resin layer provided at least at one side of the base material and containing an insulating inorganic filler, and a pressure sensitive adhesive layer provided as an outermost layer of at least one surface. According to such a pressure sensitive adhesive sheet, insulation properties can be ensured even when the base material undergoes carbonization and/or combustion/decomposition due to high temperatures and insulation breakdown occurs in the base material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application ofPCT/JP2015/065698 filed on May 29, 2015, the contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a pressure sensitive adhesive sheethaving insulation properties and preferably to a pressure sensitiveadhesive sheet used for electronic components.

BACKGROUND ART

Pressure sensitive adhesive sheets used for electronic components suchas printed circuit boards and batteries are required not to adverselyaffect the electrical characteristics of the electronic components. Forexample, pressure sensitive adhesive sheets attached to or in contactwith conductors through which electric currents flow in electroniccomponents are required to have insulation properties.

In addition, electronic components may generate heat during use. If thepressure sensitive adhesive sheets are denatured due to such heatgeneration, the electronic components may be adversely affected. Thepressure sensitive adhesive sheets used for electronic components aretherefore required to have heat resistance.

Patent Documents 1 and 2 disclose such pressure sensitive adhesivesheets used for batteries. These pressure sensitive adhesive sheets eachcomprise a base material and a pressure sensitive adhesive layerprovided on one surface of the base material.

PRIOR ART DOCUMENTS Patent Documents

[Patent Document 1] JP5639733B

[Patent Document 2] JP2011-138632A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The base material which constitutes a pressure sensitive adhesive sheetis generally formed of a material having insulation properties, but ifsuch a base material is exposed to high temperatures, carbonizationand/or combustion/decomposition (these may be referred to as“carbonization and the like,” hereinafter) may occur to change the basematerial as a whole to a conductor. In this case, the pressure sensitiveadhesive sheet exhibits conductivity and, in the electronic componentfor which the pressure sensitive adhesive sheet is used, short circuitand/or thermal runaway may occur due to the pressure sensitive adhesivesheet and a serious accident may possibly occur.

In addition, when a high voltage is applied to a part of the pressuresensitive adhesive sheet, a conductor path may be formed bycarbonization and the like of that part of the base material (insulationbreakdown). Also in this case, short circuit and/or thermal runaway mayoccur as the above and a serious accident may possibly occur.

The problems of carbonization and the like and insulation breakdown asthe above due to high temperatures cannot be sufficiently prevented byconventional pressure sensitive adhesive tapes.

The present invention has been made in consideration of such actualcircumstances and an object of the present invention is to provide apressure sensitive adhesive sheet that can ensure the insulationproperties even when the base material undergoes carbonization and/orcombustion/decomposition due to high temperatures and insulationbreakdown occurs in the base material.

Means for Solving the Problems

To achieve the above object, first, the present invention provides apressure sensitive adhesive sheet comprising: a base material havinginsulation properties; an inorganic filler-containing resin layerprovided at least at one side of the base material and containing aninsulating inorganic filler; and a pressure sensitive adhesive layerprovided as an outermost layer of at least one surface (Invention 1). Itis assumed that the outermost layer as referred to herein does notinclude a release sheet.

In the pressure sensitive adhesive sheet according to the aboveinvention (Invention 1), even when the base material is exposed to hightemperatures to change to a conductor and a high voltage is partiallyapplied to the base film to form a conductor path, the inorganic fillercontained in the inorganic filler-containing resin layer maintains theinsulation properties thereby to ensure the insulation properties of thepressure sensitive adhesive sheet itself.

In the above invention (Invention 1), the base material may preferablyhave flame retardancy that satisfies flame retardancy level V-0 of UL94standard (Invention 2).

In the above invention (Invention 1, 2), the inorganic filler-containingresin layer may preferably be provided at the one side of the basematerial and the pressure sensitive adhesive layer may preferably beprovided at a side of the inorganic filler-containing resin layeropposite to the base material (Invention 3).

In the above invention (Invention 1-3), the content of the inorganicfiller in the inorganic filler-containing resin layer may preferably be0.5-50 g/m² (Invention 4).

In the above invention (Invention 1-4), the inorganic filler-containingresin layer may preferably comprise a material obtained by curing acomposition that contains an active energy ray-curable component and theinorganic filler (Invention 5).

In the above invention (Invention 1-5), a minimum voltage at whichinsulation breakdown occurs in the base material may preferably be 1 kVor higher (Invention 6).

In the above invention (Invention 1-6), the pressure sensitive adhesivesheet may preferably be used in an electronic component (Invention 7).

Advantageous Effect of the Invention

According to the pressure sensitive adhesive sheet of the presentinvention, even when the base material undergoes carbonization and/orcombustion/decomposition due to high temperatures and insulationbreakdown occurs in the base material, the insulation properties can beensured.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a pressure sensitive adhesive sheetaccording to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a pressure sensitive adhesive sheetaccording to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of a pressure sensitive adhesive sheetaccording to still another embodiment of the present invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described.

<Pressure Sensitive Adhesive Sheet>

In an embodiment, as illustrated in FIG. 1, a pressure sensitiveadhesive sheet 1A according to the present embodiment may be composed ofa base material 11, an inorganic filler-containing resin layer 12provided at one side of the base material 11, a pressure sensitiveadhesive layer 13 provided at a side of the inorganic filler-containingresin layer 12 opposite to the base material 11, and a release sheet 14provided at a side of the pressure sensitive adhesive layer 13 oppositeto the inorganic filler-containing resin layer 12.

In another embodiment, as illustrated in FIG. 2, a pressure sensitiveadhesive sheet 1B according to the present embodiment may be composed ofa base material 11, an inorganic filler-containing resin layer 12provided at one side of the base material 11, a pressure sensitiveadhesive layer 13 provided at a side of the base material 11 opposite tothe inorganic filler-containing resin layer 12, and a release sheet 14provided at a side of the pressure sensitive adhesive layer 13 oppositeto the inorganic filler-containing resin layer 12.

In still another embodiment, as illustrated in FIG. 3, a pressuresensitive adhesive sheet 1C according to the present embodiment may becomposed of a base material 11, two inorganic filler-containing resinlayers 12 provided at both respective sides of the base material 11, apressure sensitive adhesive layer 13 provided at a side of one of theinorganic filler-containing resin layers 12 opposite to the basematerial 11, and a release sheet 14 provided at a side of the pressuresensitive adhesive layer 13 opposite to the inorganic filler-containingresin layer 12.

In the pressure sensitive adhesive sheet 1A, 1B, 1C according to thepresent embodiment, the base material 11 having insulation properties isprovided and good insulation properties are thereby exhibited under anordinary environment, that is, under a temperature at whichcarbonization and/or combustion/decomposition of the base material 11 donot occur and under an environment in which the electrical load does notcause insulation breakdown. Moreover, even when the pressure sensitiveadhesive sheet 1A, 1B, 1C is exposed to high temperatures and thematrices (organic components) in the base material 11 and/or theinorganic filler-containing resin layer 12 undergo carbonization and thelike, the insulation properties of the pressure sensitive adhesive sheet1A, 1B, 1C itself are ensured because the inorganic filler in theinorganic filler-containing resin layer 12 remains as an insulatingfilm. Furthermore, even when a high voltage is partially applied to thepressure sensitive adhesive sheet LA, 1B, 1C to flow a current throughthe pressure sensitive adhesive sheet 1A, 1B, 1C in the thicknessdirection so that the path of the current in the base material 11changes to a conductor and the matrix in the inorganic filler-containingresin layer 12 undergoes carbonization and the like along the path ofthe current, the insulation properties of the pressure sensitiveadhesive sheet 1A, 1B, 1C itself are ensured because the inorganicfiller exists as an insulating body in the path. Owing to thesefeatures, the occurrence of short circuit and/or thermal runaway issuppressed in an electronic component for which the pressure sensitiveadhesive sheet 1A, 1B, 1C is used. In specific embodiments, the pressuresensitive adhesive sheets 1A and 1C may be preferred because theinorganic filler-containing resin layer is ensured at a position nearerto an electronic component as an attachment object and an alternativepath of the conductor path due to insulation breakdown is less likely tobe formed.

1. Base Material

In the pressure sensitive adhesive sheet 1A, 1B, 1C according to thepresent embodiment, the base material 11 has insulation properties. Thebase material 11 having insulation properties allows the pressuresensitive adhesive sheet 1A, 1B, 1C to exhibit insulation propertiesduring use under an ordinary environment.

In the base material 11, the minimum voltage at which insulationbreakdown occurs may preferably be high. For example, the voltage may bepreferably 1 kV or higher, particularly preferably 2 kV or higher, andfurther preferably 5 kV or higher. When the voltage is 1 kV or higher,the insulation breakdown of the base material 11 is less likely tooccur, and the pressure sensitive adhesive sheet 1A, 18, 1C can havehigh reliability.

The base material 11 may preferably have flame retardancy that satisfiesthe flame retardancy level V-0 of the UL94 standard. Owing to such flameretardancy of the base material 11, denaturation and deformation of thebase material 11 are suppressed even when the electronic component forwhich the pressure sensitive adhesive sheet 1A, 18, 1C is used generatesheat. Moreover, even if troubles occur in the electronic component andit generates excessive heat, ignition and/or burning of the basematerial 11 are suppressed.

The material of the base material 11 is not particularly limited,provided that it can exhibit insulation properties, and can beappropriately selected from the viewpoints of the minimum voltage atwhich insulation breakdown occurs, dielectric tangent, flame retardancy,heat resistance, solvent resistance, etc. In particular, it may bepreferred to use a resin film as the base material 11. Examples of theresin film include films of polyesters such as polyethyleneterephthalate, polybutylene terephthalate and polyethylene naphthalate,polyolefin films such as a polyethylene film and polypropylene film,cellophane, a diacetyl cellulose film, triacetyl cellulose film, acetylcellulose butyrate film, polyvinyl chloride film, polyvinylidenechloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymerfilm, polystyrene film, polycarbonate film, polymethylpentene film,polysulfone film, polyether ether ketone film, polyether sulfone film,polyether imide film, fluorine resin film, polyamide film, polyimidefilm, polyamideimide film, acrylic resin film, polyurethane resin film,norbornene-based polymer film, cyclic olefin-based polymer film, cyclicconjugated diene-based polymer film, vinyl alicyclic hydrocarbon polymerfilm, other resin films, and laminated films thereof. Among these, thepolyimide film, polyetherimide film, or polyether ether ketone film maypreferably be used from the viewpoints that the heat resistance is high,the minimum voltage at which insulation breakdown occurs is high, andthe dielectric tangent is small. In particular, it may be preferred touse the polyimide film which exhibits high heat resistance. As used inthe present description, the term “polymer” encompasses the concept of a“copolymer.”

The thickness of the base material 11 may be preferably 2 μm or more,particularly preferably 6 μm or more, and further preferably 10 μm ormore. From another aspect, the thickness of the base material 11 may bepreferably 200 μm or less, particularly preferably 100 μm or less, andfurther preferably 40 μm or less. When the thickness of the basematerial 11 is 2 μm or more, the base material 11 has moderate rigidityand the occurrence of curl is effectively suppressed even if curingshrinkage occurs during the formation of the inorganic filler-containingresin layer 12 on the base material 11. On the other hand, the thicknessof the base material 11 being 200 μm or less allows the pressuresensitive adhesive sheet 1A, 1B, 1C to have moderate flexibility and,even when the pressure sensitive adhesive sheet 1A, 1B, 1C is attachedto a surface having a height difference, the pressure sensitive adhesivesheet 1A, 1B, 1C can well follow the height difference.

2. Inorganic Filler-Containing Resin Layer

(1) Composition of Inorganic Filler-Containing Resin Layer

The inorganic filler-containing resin layer 12 contains an insulatinginorganic filler. When the inorganic filler-containing resin layer 12contains an insulating inorganic filler, even in a case in which thematrices in the base material 11 and/or the inorganic filler-containingresin layer 12 undergo carbonization and/or combustion/decomposition dueto high temperatures, the inorganic filler in the inorganicfiller-containing resin layer 12 remains as an insulating film.Moreover, even when the insulation breakdown occurs in the base material11 and the matrix in the inorganic filler-containing resin layer 12undergoes carbonization and the like along the path of the insulationbreakdown, the inorganic filler exists as an insulating body in thepath. Owing to these features, the insulation properties of the pressuresensitive adhesive sheet 1A, 1B, 1C itself is ensured.

The inorganic filler-containing resin layer 12 may preferably be formedof a composition that contains an organic component and an inorganicfiller (this composition may be referred to as a “composition forinorganic filler-containing resin layer,” hereinafter). In particular,the inorganic filler-containing resin layer may preferably be a hardcoat layer from the viewpoint of heat resistance. The hard coat layermay preferably be made of a material obtained by curing a compositionthat contains an active energy ray-curable component and an inorganicfiller. In the pressure sensitive adhesive sheet 1C illustrated in FIG.3, the composition may be the same or different in the two inorganicfiller-containing resin layers 12.

(1-1) Active Energy Ray-Curable Component

The active energy ray-curable component is not particularly limited,provided that it can be cured by irradiation with active energy rays toexhibit desired hardness.

Specific examples of the active energy ray-curable component include apolyfunctional (meth)acrylate-based monomer, (meth)acrylate-basedprepolymer, and active energy ray-curable polymer, among which thepolyfunctional (meth)acrylate-based monomer and/or (meth)acrylate-basedprepolymer may be preferred. The polyfunctional (meth)acrylate-basedmonomer and the (meth)acrylate-based prepolymer may each be used aloneand both may also be used in combination. As used in the presentdescription, the (meth)acrylate refers to both an acrylate and amethacrylate. The same applies to other similar terms.

Examples of the polyfunctional (meth)acrylate-based monomer include1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate,hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyldi(meth)acrylate, caprolactone-modified dicyclopentenyldi(meth)acrylate, ethylene oxide-modified phosphoric aciddi(meth)acrylate, allylated cyclohexyl di(meth)acrylate, isocyanuratedi(meth)acrylate, trimethylol propane tri(meth)acrylate,dipentaerythritol tri(meth)acrylate, propionic acid-modifieddipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate,propylene oxide-modified trimethylolpropane tri(meth)acrylate,tris(acryloxyethyl)isocyanurate, propionic acid-modifieddipentaerythritol penta(meth)acrylate, dipentaerythritolhexa(meth)acrylate, caprolactone-modified dipentaerythritolhexa(meth)acrylate, and other appropriate polyfunctional(meth)acrylates. These may each be used alone and two or more types mayalso be used in combination.

On the other hand, examples of the (meth)acrylate-based prepolymerinclude polyester acrylate-based, epoxy acrylate-based, urethaneacrylate-based, and polyol acrylate-based prepolymers. One type ofprepolymer may be used alone and two or more types may also be used incombination.

A (meth)acrylic ester polymer having an active energy ray-curable groupat a side chain (referred to as an “active energy ray-curable(meth)acrylic ester polymer (A),” hereinafter) can be used as the activeenergy ray-curable polymer. The active energy ray-curable (meth)acrylicester polymer (A) may preferably be obtained by reacting anacrylic-based polymer (a1) having a functional group-containing monomerunit and an unsaturated group-containing compound (a2) having asubstituent group that is bonded to the functional group. Preferredexamples of the unsaturated group include (meth)acryloyl group.

When the inorganic filler-containing resin layer 12 of the presentembodiment is a hard coat layer, the glass-transition point after curingof the active energy ray-curable component which constitutes the hardcoat layer may be preferably 130° C. or higher and more preferably 150°C. or higher, and an active energy ray-curable component of which theglass-transition point is not observed may be particularly preferred.When the glass-transition point of the active energy ray-curablecomponent satisfies the above, the hard coat layer has excellent heatresistance, and an electronic component that includes the pressuresensitive adhesive sheet 1A, 18B, 1C provided with such a hard coatlayer can have excellent performance and safety.

When two or more types of the active energy ray-curable components areused in the hard coat layer of the present embodiment, it may bepreferred for them to have excellent compatibility with each other.

(1-2) Other Organic Components

Examples of organic components that can be used other than the activeenergy ray-curable component include a thermoset resin and athermoplastic resin. By compounding such components, interfacialadhesion between the inorganic filler-containing resin layer 12 and thebase material 11 can be made higher. Specific examples of such organiccomponents include a polyamide imide resin, polyether imide resin,polyimide resin, polyarylate resin, polyether ether ketone resin,polysulfone resin, melamine resin, and phenol resin. Among these, thepolyamide imide resin may be preferred because of its excellent heatresistance.

(1-3) Inorganic Filler

The content of the inorganic filler in the inorganic filler-containingresin layer 12 may be preferably 0.5-50 g/m², particularly preferably0.5-10 g/m², and further preferably 0.5-2 g/m². When the content of theinorganic filler is 0.5 g/m² or more, even in a case in which thematrices in the base material 11 and/or the inorganic filler-containingresin layer 12 undergo carbonization and/or combustion/decomposition dueto high temperatures, the inorganic filler in the inorganicfiller-containing resin layer 12 well remains as an insulating film.Moreover, even when the insulation breakdown occurs in the base material11 and the matrix in the inorganic filler-containing resin layer 12undergoes carbonization and the like along the path of the insulationbreakdown, the inorganic filler well exists as an insulating body in thepath. Owing to these features, the insulation properties of the pressuresensitive adhesive sheet 1A, 1B, 1C itself can be ensured. When thecontent of the inorganic filler is 50 g/m² or less, the production costis avoided from being unduly high and it is easy to form a layer usingthe composition for inorganic filler-containing resin layer. The contentof the inorganic filler in the inorganic filler-containing resin layer12 can be appropriately controlled by adjusting the addition amount ofthe inorganic filler in the composition for inorganic filler-containingresin layer and/or the thickness of the inorganic filler-containingresin layer 12.

When the inorganic filler-containing resin layer 12 is formed using thecomposition for inorganic filler-containing resin layer, the content ofthe inorganic filler in the composition for inorganic filler-containingresin layer may be preferably 1-99 mass %, particularly preferably 10-90mass %, and further preferably 45-75 mass %.

The inorganic filler is not restricted, provided that it has insulationproperties. Examples of the inorganic filler include powders of silica,alumina, boehmite, talc, calcium carbonate, titanium oxide, iron oxide(III), silicon carbide, boron nitride, zirconium oxide and otherappropriate materials, spherical beads thereof, single crystal fibers,and glass fibers. These can each be used alone and two or more types canalso be used in combination. Among these, silica, alumina, boehmite,titanium oxide, zirconium oxide and the like may be preferred. From theviewpoint of insulation properties, silica and alumina may be preferredand silica may be particularly preferred.

It may also be preferred for the inorganic filler to besurface-modified. A reactive silica can be exemplified as the preferredinorganic filler which is surface-modified.

As used in the present description, the “reactive silica” refers tosilica fine particles that are surface-modified with an organic compoundhaving an active energy ray-curable unsaturated group. The above silicafine particles (reactive silica) which are surface-modified with anorganic compound having an active energy ray-curable unsaturated groupmay ordinarily be obtained, for example, by a reaction between silanolgroups on the surfaces of silica fine particles and an active energyray-curable unsaturated group-containing organic compound havingfunctional groups (such as isocyanate groups, epoxy groups, and carboxygroups) that can react with the silanol groups. The average diameter ofthe silica fine particles may be about 0.5-500 nm and preferably 1-200nm. Preferred examples of the above active energy ray-curableunsaturated group include a (meth)acryloyl group and a vinyl group.

Examples to be preferably used as the active energy ray-curableunsaturated group-containing organic compound having functional groupsthat can react with the silanol groups include compounds or the likerepresented by General Formula (I).

(In the formula, R¹ represents a hydrogen atom or a methyl group and R²represents a halogen atom,

Available examples of such compounds include (meth)acrylic acid andderivatives of (meth)acrylic acid, such as (meth)acrylic chloride,(meth)acryloyloxyethyl isocyanate, glycidyl (meth)acrylate,2,3-iminopropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, andacryloyloxypropyltrimethoxysilane. These (meth)acrylic acid derivativesmay each be used alone and two or more types may also be used incombination.

Commercially-available examples of an organic-inorganic hybrid material(organosilica sol) that contains such an reactive silica and thepreviously-described polyfunctional (meth)acrylate-based monomer and/or(meth)acrylate-based prepolymer include products of the trade name“OPSTAR Z7530,” “OPSTAR Z7524,” “OPSTAR TU4086,” and “OPSTAR Z7537” (allavailable from JSR Corporation).

Other examples of preferred inorganic fillers include alumina ceramicnanoparticles, a silica sol in which silica fine particles havingsilanol groups exposed at the silica surface are suspended in acolloidal state in the dispersion medium, and an organosilica sol inwhich silanol groups on the silica surface are surface-treated with asilane coupling agent or the like.

The average particle diameter of the inorganic filler used in thepresent embodiment may be preferably 1-1,000 nm, particularly preferably10-500 nm, and further preferably 20-200 nm. When the average particlediameter of the inorganic filler is 1 nm or more, the inorganicfiller-containing resin layer 12 obtained by curing the composition forinorganic filler-containing resin layer has more stable insulationproperties. When the average particle diameter of the inorganic filleris 1,000 nm or less, the dispersibility of the inorganic filler in thecomposition for inorganic filler-containing resin layer is excellent andit is thus possible to effectively prevent the occurrence ofirregularities on the surface of the inorganic filler-containing resinlayer 12 opposite to the base material 11 during the formation of theinorganic filler-containing resin layer 12 on the base material 11.Moreover, when the pressure sensitive adhesive layer 13 is formed onthat surface, significantly high smoothness can be obtained on thesurface of the pressure sensitive adhesive layer 13 opposite to theinorganic filler-containing resin layer 12. This allows the pressuresensitive adhesive layer 13 to exhibit an excellent adhesion property toan adherend. The average particle diameter of the inorganic filler is tobe measured using a zeta potential measurement method.

(1-4) Other Components

The composition for forming the inorganic filler-containing resin layer12 of the present embodiment may contain various additives in additionto the above-described components. Examples of such additives include aphotopolymerization initiator, antioxidant, antistatic, silane couplingagent, antiaging agent, thermal polymerization inhibitor, colorant,surfactant, storage stabilizer, plasticizer, glidant, antifoam, andorganic-based filler.

When the inorganic filler-containing resin layer 12 is a hard coatlayer, it is preferred to use a photopolymerization initiator togetherwith the active energy ray-curable component in the hard coat layer. Thephotopolymerization initiator is not particularly limited, provided thatit functions as a photopolymerization initiator for the active energyray-curable component to be used. Examples of the photopolymerizationinitiator include acylphosphine oxide-based compounds, benzoincompounds, acetophenone compounds, titanocene compounds, thioxanthonecompounds, and peroxide compounds. Specific examples include1-hydroxycyclohexyl phenyl ketone,2-hydroxy-2-methyl-1-phenyl-propane-1-one,2,2-dimethoxy-1,2-diphenylethan-1-one, benzoin, benzoin methyl ether,benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide,tetramethyl thiuram monosulfide, azobisisobutyronitrile, dibenzyl,diacetyl, and β-chloroanthraquinone.

The content of the above photopolymerization initiator may be preferably0.1-20 mass parts in general and particularly preferably 1-15 mass partsto 100 mass parts of the active energy ray-curable component.

(2) Physical Properties of Hard Coat Layer as InorganicFiller-Containing Resin Layer

In the pressure sensitive adhesive sheet 1A, 1B, 1C according to thepresent embodiment, when the inorganic filler-containing resin layer 12is a hard coat layer, the pencil hardness of the hard coat layer in astate of being formed on the base material 11 may be preferably HB ormore and particularly preferably H or more as measured in accordancewith JIS K5600-5-4. When the hard coat layer has such pencil hardness,excellent heat resistance can be exhibited. The upper limit of thepencil hardness of the hard coat layer is not particularly restricted,but may be preferably 9H or less, particularly preferably 6H or less,and further preferably 3H or less from the viewpoint of obtainingexcellent following ability to a height difference. In the pressuresensitive adhesive sheet 1C illustrated in FIG. 3, the pencil hardnessof the two hard coat layers may be the same or different. The pencilhardness of the hard coat layer or layers is as described in theexemplary test, which will be described later.

(3) Thickness of Inorganic Filler-Containing Resin Layer

The thickness of the inorganic filler-containing resin layer 12 may bepreferably 0.1 μm or more, particularly preferably 0.5 μm or more, andfurther preferably 1 μm or more. From another aspect, the thickness ofthe inorganic filler-containing resin layer 12 may be preferably 10 μmor less, particularly preferably 7 μm or less, and further preferably 4μm or less. When the thickness of the inorganic filler-containing resinlayer 12 is 0.1 μm or more, the insulation properties by the inorganicfiller can be effectively exhibited even in cases in which the basematerial 11 undergoes carbonization and/or combustion/decomposition dueto high temperatures and insulation breakdown occurs in the basematerial 11. On the other hand, the thickness of the inorganicfiller-containing resin layer 12 being 10 μm or less allows the pressuresensitive adhesive sheet 1A, 1B, 1C to have moderate flexibility and,even when the pressure sensitive adhesive sheet 1A, 1B, 1C is attachedto a surface having a height difference, the pressure sensitive adhesivesheet 1A, 1B, 1C can well follow the height difference. In the pressuresensitive adhesive sheet 1C illustrated in FIG. 3, the thicknesses ofthe two inorganic filler-containing resin layer 12 may be the same ordifferent.

3. Pressure Sensitive Adhesive Layer

In the pressure sensitive adhesive sheet 1A, 1B, 1C according to thepresent embodiment, the pressure sensitive adhesive layer 13 is providedas an outermost layer (extruding a release sheet) of at least onesurface. The pressure sensitive adhesive sheet 1A, 1B, and 1Cillustrated respectively in FIGS. 1 to 3 each have one pressuresensitive adhesive layer 13, but may each be provided with an additionalpressure sensitive adhesive layer 13. For example, in the pressuresensitive adhesive sheet 1A illustrated in FIG. 1, an additionalpressure sensitive adhesive layer 13 may be added on the surface of thebase material 11 opposite to the inorganic filler-containing resin layer12. In the pressure sensitive adhesive sheet 1B illustrated in FIG. 2,an additional pressure sensitive adhesive layer 13 may be added on thesurface of the inorganic filler-containing resin layer 12 opposite tothe base material 11. In the pressure sensitive adhesive sheet 1Cillustrated in FIG. 3, an additional pressure sensitive adhesive layer13 may be added on the surface, opposite to the base material 11, of theinorganic filler-containing resin layer 12 located at the upper side inthe figure.

(1) Composition of Pressure Sensitive Adhesive Layer

The pressure sensitive adhesive which constitutes the pressure sensitiveadhesive layer 13 is not particularly limited and can be appropriatelyselected from the viewpoints of flame retardancy, heat resistance,insulating properties, and the like. In particular, an acrylic-basedpressure sensitive adhesive, silicone-based pressure sensitive adhesive,rubber-based pressure sensitive adhesive, and urethane-based pressuresensitive adhesive may be preferred as the pressure sensitive adhesivewhich constitutes the pressure sensitive adhesive layer 13. Among these,the acrylic-based pressure sensitive adhesive may be particularlypreferred from the viewpoints of an adhesion property to the inorganicfiller-containing resin layer 12, an electrode and the like, easydelicate adjustment of the storage elastic modulus at 120° C. andadhesive strength of the pressure sensitive adhesive layer 13, etc. Thestorage elastic modulus at 120° C. of the pressure sensitive adhesivelayer 13 will be described later.

(1-1) Acrylic-Based Pressure Sensitive Adhesive

The acrylic-based pressure sensitive adhesive may preferably contain a(meth)acrylic ester polymer and particularly preferably contain acompound in which the (meth)acrylic ester polymer is crosslinked by acrosslinker.

The (meth)acrylic ester polymer may preferably contain a (meth)acrylicalkyl ester of which the carbon number of alkyl group is 1-20, as amonomer that constitutes the polymer. This allows the obtained pressuresensitive adhesive to exhibit a preferred pressure sensitive adhesiveproperty. The (meth)acrylic ester polymer may be particularly preferablya copolymer of a (meth)acrylic alkyl ester of which the carbon number ofalkyl group is 1-20, a monomer having a functional group that reactswith the crosslinker (reactive functional group-containing monomer), andother monomers that may be used as desired.

Examples of the (meth)acrylic alkyl ester of which the carbon number ofalkyl group is 1-20 include methyl (meth)acrylate, ethyl (meth)acrylate,propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate,n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl(meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate,myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl(meth)acrylate. Among these, (meth)acrylic alkyl ester of which thecarbon number of alkyl group is 1-8 may be preferred from the viewpointof further improving the pressure sensitive adhesive property, and themethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl(meth)acrylate may be particularly preferred. These may each be usedalone and two or more types may also be used in combination.

The (meth)acrylic ester polymer may preferably contain 40-99 mass %,particularly preferably contain 50-90 mass %, and further preferablycontain 75-85 mass % of the (meth)acrylic alkyl ester of which thecarbon number of alkyl group is 1-20, as the monomer unit whichconstitutes the polymer.

Preferred examples of the above reactive functional group-containingmonomer include a monomer having a hydroxy group in the molecule(hydroxy group-containing monomer), a monomer having a carboxy group inthe molecule (carboxyl group-containing monomer), and a monomer havingan amino group in the molecule (amino group-containing monomer). Thesemay each be used alone and two or more types may also be used incombination.

Examples of the hydroxy group-containing monomer include hydroxyalkyl(meth)acrylate, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl(meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl(meth)acrylate. Among these, the 2-hydroxyethyl (meth)acrylate and4-hydroxybutyl (meth)acrylate may be preferred from the viewpoints ofreactivity of the hydroxy group with the crosslinker in the(meth)acrylic ester polymer to be obtained and copolymerizability withother monomers. These may each be used alone and two or more types mayalso be used in combination.

Examples of the carboxy group-containing monomer includeethylenically-unsaturated carboxylic acid, such as acrylic acid,methacrylic acid, crotonic acid, maleic acid, itaconic acid, andcitraconic acid. Among these, the acrylic acid may be preferred from theviewpoints of reactivity of the carboxy group with the crosslinker inthe (meth)acrylic ester polymer to be obtained and copolymerizabilitywith other monomers. These may each be used alone and two or more typesmay also be used in combination.

Examples of the amino group-containing monomer include aminoethyl(meth)acrylate and n-butylaminoethyl (meth)acrylate. These may each beused alone and two or more types may also be used in combination.

The (meth)acrylic ester polymer may preferably contain 0.1-40 mass %,particularly preferably contain 0.5-20 mass %, and further preferablycontain 1.0-4.0 mass % of the reactive functional group-containingmonomer. When the content of the reactive functional group-containingmonomer is 0.1 mass % or more, it is possible to effectively improve thecohesive strength of the pressure sensitive adhesive obtained byconstituting a crosslinked structure via a crosslinker which will bedescribed later. When the content is 40 mass % or less, a desiredpressure sensitive adhesive property may readily be obtained.

Examples of the above other monomers include alkoxyalkyl (meth)acrylate,such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate,(meth)acrylate having an aliphatic ring, such as cyclohexyl(meth)acrylate, non-crosslinkable acrylamide, such as acrylamide andmethacrylamide, (meth)acrylate having a non-crosslinkable tertiary aminogroup, such as N,N-dimethylaminoethyl (meth)acrylate andN,N-dimethylaminopropyl (meth)acrylate, vinyl acetate, and styrene.These may each be used alone and two or more types may also be used incombination.

The polymerization form of the (meth)acrylic ester polymer may be arandom copolymer and may also be a block copolymer.

The weight-average molecular weight of the (meth)acrylic ester polymermay be preferably 300,000-2,500,000, particularly preferably400,000-1,900,000, and further preferably 700,000-1,600,000. When theweight-average molecular weight of the (meth)acrylic ester polymer is300,000 or more, the durability of the pressure sensitive adhesive layer13 is excellent. When the weight-average molecular weight of the(meth)acrylic ester polymer is 2,500,000 or less, good coatingproperties are obtained. As used in the present description, theweight-average molecular weight refers to a standard polystyreneequivalent value that is measured using a gel permeation chromatography(GPC) method.

In the above acrylic-based pressure sensitive adhesive, one type of the(meth)acrylic ester polymer may be used alone and two or more types mayalso be used in combination.

It suffices that the crosslinker is reactive with a reactive functionalgroup of the (meth)acrylic ester polymer. Examples of the crosslinkerinclude an isocyanate-based crosslinker, epoxy-based crosslinker,amine-based crosslinker, melamine-based crosslinker, aziridine-basedcrosslinker, hydrazine-based crosslinker, aldehyde-based crosslinker,oxazoline-based crosslinker, metal alkoxide-based crosslinker, metalchelate-based crosslinker, metal salt-based crosslinker, and ammoniumsalt-based crosslinker. One type of the crosslinker may be used aloneand two or more types may also be used in combination.

The isocyanate-based crosslinker contains at least a polyisocyanatecompound. Examples of the polyisocyanate compound include aromaticpolyisocyanates such as tolylene diisocyanate, diphenylmethanediisocyanate and xylylene diisocyanate, aliphatic polyisocyanates suchas hexamethylene diisocyanate, alicyclic polyisocyanates such asisophorone diisocyanate and hydrogenated diphenylmethane diisocyanate,biuret bodies and isocyanurate bodies thereof, and adduct bodies thatare reaction products with low molecular active hydrogen-containingcompounds such as ethylene glycol, propylene glycol, neopentyl glycol,trimethylol propane, and castor oil. Among these,trimethylolpropane-modified aromatic polyisocyanate may be preferred andtrimethylolpropane-modified tolylene diisocyanate andtrimethylolpropane-modified xylylene diisocyanate may be particularlypreferred from the viewpoint of reactivity with hydroxy groups.

The amount of the crosslinker to be used may be preferably 0.001-10 massparts, particularly preferably 0.01-5 mass parts, and further preferably1-3 mass parts to 100 mass parts of the (meth)acrylic ester polymer.

When the pressure sensitive adhesive composition which contains acrosslinker and a (meth)acrylic ester polymer that contains a reactivefunctional group-containing monomer as a monomer unit constituting thepolymer is subjected to heating or the like, the crosslinker reacts withthe reactive functional group of the reactive functionalgroup-containing monomer which constitutes the (meth)acrylic esterpolymer. This allows a structure to be formed in which the (meth)acrylicester polymer is crosslinked by the crosslinker. The gel fraction of theobtained pressure sensitive adhesive can thus be set to a desired value,and the cohesive strength of the pressure sensitive adhesive andtherefore the strength and durability are improved.

If desired, the above acrylic-based pressure sensitive adhesive maycontain various commonly-used additives, such as a refractive indexadjuster, antistatic, tackifier, silane coupling agent, antioxidant,ultraviolet absorber, light stabilizer, softening agent, filler, lightcuring agent, and photopolymerization initiator.

(1-2) Silicone-Based Pressure Sensitive Adhesive

The silicone-based pressure sensitive adhesive may preferably contain anorganopolysiloxane, in particular, an addition-type organopolysiloxane(a cured product thereof). The addition-type organopolysiloxane maypreferably be obtained through a reaction between an organopolysiloxaneof which the main skeleton is a siloxane bond and which has an alkenylgroup and an organohydrogenpolysiloxane.

The organopolysiloxane of which the main skeleton is a siloxane bond andwhich has an alkenyl group may preferably be a compound that isrepresented by the following average unit formula (II) and has at leasttwo alkenyl groups in the molecule.R¹aSiO_((4-a)/2)  (II)(In the formula, each R¹ is independently the same or differentunsubstituted or substituted monovalent hydrocarbon group of which thecarbon number is 1-12 and preferably 1-8, and “a” is a positive numberof 1.5-2.8, preferably 1.8-2.5, and more preferably 1.95-2.05.)

Examples of the above unsubstituted or substituted monovalenthydrocarbon group represented by R¹ bonded to the silicon atom includealkenyl groups such as a vinyl group, allyl group, propenyl group,isopropenyl group, butenyl group, hexenyl group, cyclohexenyl group andoctenyl group, alkyl groups such as a methyl group, ethyl group, propylgroup, isopropyl group, butyl group, isobutyl group, tert-butyl group,pentyl group, neopentyl group, hexyl group, cyclohexyl group, octylgroup, nonyl group and decyl group, aryl groups such as a phenyl group,tolyl group, xylyl group and naphthyl group, aralkyl groups such as abenzyl group, phenylethyl group and phenylpropyl group, and thoseobtained by substituting a part or all of the hydrogen atoms of thesegroups with halogen atoms such as fluorine, bromine and chlorine, cyanogroups, or other appropriate groups, for example, a chloromethyl group,chloropropyl group, bromoethyl group, trifluoropropyl group, cyanoethylgroup, and the like. The alkenyl group may preferably be a vinyl groupfrom the viewpoint of reducing the curing time and high productivity.

The organohydrogenpolysiloxane has a SiH group in the molecule. Theabove alkenyl group of the organopolysiloxane and the SiH group of theorganohydrogenpolysiloxane react with each other through an additionreaction and an addition-type organopolysiloxane can thereby beobtained.

The addition-type organopolysiloxane is well cured in the presence of aplatinum catalyst and, therefore, the above silicone-based pressuresensitive adhesive may preferably contain a platinum catalyst. Examplesof the platinum catalyst include platinum black, platinum chloride,chloroplatinic acid, a reaction product of chloroplatinic acid andmonohydric alcohol, a complex of chloroplatinic acid and olefins, andplatinum bisacetoacetate.

The content of the platinum catalyst in the above silicone-basedpressure sensitive adhesive may be preferably 0.01-3 mass parts andparticularly preferably 0.05-2 mass parts to 100 mass parts of theaddition-type organopolysiloxane. The content of the platinum catalystbeing within the above range allows the addition-type organopolysiloxaneto be cured without interfering with the coating, and the pressuresensitive adhesive layer 13 can thus be formed.

The addition-type organopolysiloxane can contain an organopolysiloxane(silicone resin) that contains a trifunctional or tetrafunctionalsiloxane unit in the molecule in order to increase the adhesivestrength.

The content of the organopolysiloxane, which contains a trifunctional ortetrafunctional siloxane unit, in the above silicone-based pressuresensitive adhesive may be preferably 0-100 mass parts, particularlypreferably 5-70 mass parts, and further preferably 10-50 mass parts to100 mass parts of the addition-type organopolysiloxane.

(1-3) Rubber-Based Pressure Sensitive Adhesive

The rubber-based pressure sensitive adhesive may preferably contain anA-B-A-type block copolymer as a rubber elastic component and a tackifierand, if desired, further contain an antioxidant for preventingdeterioration.

Examples of the A-B-A-type block copolymer include astyrene-isoprene-styrene copolymer, styrene-butylene-styrene copolymer,styrene-ethylene-butylene-styrene copolymer, styrene-olefin-styrenecopolymer, polyisoprene, polybutene, and polyisobutylene.

The content of the rubber elastic component in the rubber-based pressuresensitive adhesive may be preferably 5-50 mass % and particularlypreferably 7-45 mass %. When the content of the rubber elastic componentis 5 mass % or more, the cohesive strength of the rubber-based pressuresensitive adhesive can be maintained high, while when the content of therubber elastic component is 50 mass % or less, the adhesive strength ofthe pressure sensitive adhesive layer can be moderately high.

Examples of the tackifier include a rosin-based resin, polyterpene-basedresin, coumarone/indene resin, petroleum-based resin, terpene phenolresin, alkylphenol resin, styrene-based resin, phenol-based resin, andxylene resin.

The content of the tackifier in the rubber-based pressure sensitiveadhesive may be preferably 10-70 mass % and particularly preferably15-60 mass %. If the content of the tackifier is less than 10 mass %,the adhesive strength of the pressure sensitive adhesive layerdecreases, while if the content of the tackifier exceeds 70 mass %, thecohesive strength of the rubber-based pressure sensitive adhesive may beunduly low.

Examples of the antioxidant include butylhydroxytoluene,2,6-di-t-butyl-4-methylphenol, 2,5-di-t-butylhydroquinone,mercaptobenzimidazole, 1,1-bis(4-hydroxyphenol)cyclohexane, andphenyl-β-naphthylamine.

When an antioxidant is used, the content of the antioxidant in therubber-based pressure sensitive adhesive may be preferably 0.1-10 mass %and particularly preferably 0.2-5 mass %.

(2) Physical Properties of Pressure Sensitive Adhesive/PressureSensitive Adhesive Layer

In the pressure sensitive adhesive sheet 1A, 1B, 1C according to thepresent embodiment, the storage elastic modulus at 120° C. of thepressure sensitive adhesive layer 13 may be preferably 1-500 kPa,particularly preferably 10-200 kPa, and further preferably 40-100 kPa.When the storage elastic modulus is within the above range, the pressuresensitive adhesive layer 13 has sufficient hardness even under acondition of relatively high temperatures. Thus, even when pressure isapplied to the pressure sensitive adhesive sheet 1A, 1B, 1C, thepressure sensitive adhesive layer 13 is less likely to deform andprotrude from the base material 11 and the inorganic filler-containingresin layer 12. This suppresses the occurrence of troubles in anelectronic component due to the pressure sensitive adhesive layer 13. Amethod of measuring the storage elastic modulus at 120° C. of thepressure sensitive adhesive layer 13 is as described in the exemplarytest, which will be described later.

In the pressure sensitive adhesive sheet 1A, 1B, 1C according to thepresent embodiment, the gel fraction of the pressure sensitive adhesivewhich constitutes the pressure sensitive adhesive layer 13 maypreferably be 20-100%. In particular, when the pressure sensitiveadhesive which constitutes the pressure sensitive adhesive layer 13 isan acrylic-based pressure sensitive adhesive, the gel fraction may bepreferably 20-98%, particularly preferably 50-95%, and furtherpreferably 70-85%. The gel fraction being 20% or more allows thepressure sensitive adhesive to have sufficient cohesive strength. On theother hand, the gel fraction being 98% or less allows the pressuresensitive adhesive sheet 1A, 1B, 1C to have moderate flexibility and,even when the pressure sensitive adhesive sheet 1A, 1B, 1C is attachedto a surface having a height difference, the pressure sensitive adhesivesheet 1A, 1B, 1C can well follow the height difference. A method ofmeasuring the gel fraction is as described in the exemplary test, whichwill be described later.

(3) Thickness of Pressure Sensitive Adhesive Layer

The thickness of the pressure sensitive adhesive layer 13 may bepreferably 1 μm or more, particularly preferably 3 μm or more, andfurther preferably 4 μm or more. From another aspect, the thickness ofthe pressure sensitive adhesive layer 13 may be preferably 50 μm orless, particularly preferably 15 μm or less, and further preferably 9 μmor less. When the thickness of the pressure sensitive adhesive layer 13is 1 μm or more, the pressure sensitive adhesive sheet 1A, 18, 1C canexhibit sufficient adhesive strength. When the thickness of the pressuresensitive adhesive layer 13 is 50 μm or less, it is possible to preventmixture or the like of the residual solvent and bubbles into thepressure sensitive adhesive layer 13 and easily adjust theabove-described storage elastic modulus and the adhesive strength, whichwill be described later.

4. Release Sheet

The release sheet 14 is to protect the pressure sensitive adhesive layeruntil the use of the pressure sensitive adhesive sheet 1A, 1B, 1C and isremoved when using the pressure sensitive adhesive sheet 1A, 1B, 1C. Inthe pressure sensitive adhesive sheet 1A, 1B, 1C according to thepresent embodiment, the release sheet 14 may not necessarily berequired.

Examples of the release sheet 14 to be used include a polyethylene film,polypropylene film, polybutene film, polybutadiene film,polymethylpentene film, polyvinyl chloride film, vinyl chloridecopolymer film, polyethylene terephthalate film, polyethylenenaphthalate film, polybutylene terephthalate film, polyurethane film,ethylene-vinyl acetate film, ionomer resin film, ethylene-(meth)acrylicacid copolymer film, ethylene-(meth)acrylic ester copolymer film,polystyrene film, polycarbonate film, polyimide film, fluorine resinfilm, and liquid crystal polymer film. Crosslinked films thereof mayalso be used. A laminate film obtained by laminating a plurality of suchfilms may also be used.

It may be preferred to perform release treatment for the release surface(surface to be in contact with the pressure sensitive adhesive layer 13)of the release sheet 14. Examples of a release agent to be used for therelease treatment include alkyd-based, silicone-based, fluorine-based,unsaturated polyester-based, polyolefin-based, and wax-based releaseagents.

The thickness of the release sheet 14 is not particularly restricted,but may ordinarily be about 20-150 μm.

5. Physical Properties Etc. Of Pressure Sensitive Adhesive Sheet

The adhesive strength of the pressure sensitive adhesive sheet 1A, 1B,1C according to the present embodiment to an aluminum plate may bepreferably 0.1-20 N/25 mm, particularly preferably 0.5-10 N/25 mm, andfurther preferably 1-5 N/25 mm. As used herein, the adhesive strengthrefers basically to a peel strength that is measured using a method of180° peeling in accordance with JIS Z0237: 2009. Details of the methodof measurement are as described in the exemplary test, which will bedescribed later.

The thickness of the pressure sensitive adhesive sheet 1A, 1B, 1Cwithout the release sheet may be preferably 5-250 μm, particularlypreferably 10-110 μm, and further preferably 15-45 μm.

<Method of Manufacturing Pressure Sensitive Adhesive Sheet>

The pressure sensitive adhesive sheet 1A according to the presentembodiment can be manufactured, for example, through producing alaminate of the base material 11 and the inorganic filler-containingresin layer 12 and a laminate of the pressure sensitive adhesive layer13 and the release sheet 14 and attaching these laminates to each otherso that the inorganic filler-containing resin layer 12 comes intocontact with the pressure sensitive adhesive layer 13.

The pressure sensitive adhesive sheet 18B according to the presentembodiment can be manufactured, for example, through producing alaminate of the base material 11 and the inorganic filler-containingresin layer 12 and a laminate of the pressure sensitive adhesive layer13 and the release sheet 14 and attaching these laminates to each otherso that the base material 11 comes into contact with the pressuresensitive adhesive layer 13.

The pressure sensitive adhesive sheet 1C according to the presentembodiment can be manufactured, for example, through producing alaminate in which both surfaces of the base material 11 are formed withthe inorganic filler-containing resin layers 12 and a laminate of thepressure sensitive adhesive layer 13 and the release sheet 14 andattaching these laminates to each other so that one of the inorganicfiller-containing resin layers 12 comes into contact with the pressuresensitive adhesive layer 13.

From the viewpoint of enhancing the interfacial adhesion between theinorganic filler-containing resin layer 12 and the pressure sensitiveadhesive layer 13, it may be preferred to perform surface treatment suchas corona treatment and plasma treatment for a surface to be attached ofany one of these layers or surfaces to be attached of both of theselayers and then attach these layers to each other.

The laminate of the base material 11 and the inorganic filler-containingresin layer 12 can be produced, for example, in the following manner.First, one main surface of the base material 11 may be coated with acoating agent that contains the composition for inorganicfiller-containing resin layer and may further contain a solvent ifdesired, and the coating agent may be dried. The method of coating withthe coating agent may be performed using an ordinary method, such as abar coating method, knife coating method, Meyer bar method, roll coatingmethod, blade coating method, die coating method, and gravure coatingmethod. Drying can be performed, for example, by heating at 80-150° C.for about 30 seconds to 5 minutes.

Thereafter, the layer obtained by drying the above coating agent may beirradiated with active energy rays to cure the layer to form theinorganic filler-containing resin layer 12. As the active energy rays,for example, electromagnetic wave or charged particle radiation havingan energy quantum can be used and, specifically, ultraviolet rays,electron rays or the like can be used. In particular, ultraviolet raysmay be preferred because of easy management. Irradiation withultraviolet rays can be performed using a high pressure mercury lamp,xenon lamp or the like, and the irradiance level of ultraviolet rays maybe preferably about 50-1,000 mW/cm² as the illuminance. The light amountmay be preferably 50-10,000 mJ/cm², more preferably 80-5,000 mJ/cm², andparticularly preferably 200-2,000 mJ/cm². On the other hand, irradiationwith electron rays can be performed using an electron ray accelerator orthe like, and the irradiance level of electron rays may be preferablyabout 10-1,000 krad.

The laminate of the pressure sensitive adhesive layer 13 and the releasesheet 14 can be produced, for example, in the following manner.

When the pressure sensitive adhesive layer 13 is formed using anacrylic-based pressure sensitive adhesive, the release surface of therelease sheet 14 may be coated with a coating solution that contains theabove-described acrylic-based pressure sensitive adhesive and mayfurther contain a solvent if desired, and heating treatment may beperformed to form a coating film. The formed coating film itself may bethe pressure sensitive adhesive layer 13 if an aging period is notnecessary. If the aging period is necessary, the formed coating film maybecome the pressure sensitive adhesive layer 13 after the aging periodpasses.

Drying treatment when volatilizing a diluent solvent and the like of thecoating solution can also serve as the above heating treatment. Whenperforming the heating treatment, the heating temperature may bepreferably 50-150° C. and particularly preferably 70-120° C. The heatingtime may be preferably 30 seconds to 10 minutes and particularlypreferably 50 seconds to 2 minutes. If necessary, an aging period may beprovided after the heating treatment at an ordinary temperature (e.g.23° C. and 50% RH) for one to two weeks. When the acrylic-based pressuresensitive adhesive contains a (meth)acrylic ester polymer having areactive functional group and a crosslinker, the heating treatmentallows a structure to be formed in which the (meth)acrylic ester polymeris crosslinked by the crosslinker.

When the pressure sensitive adhesive layer 13 is formed using asilicone-based pressure sensitive adhesive, the release surface of therelease sheet 14 may be coated with a coating solution, which is thenheated for curing to form the pressure sensitive adhesive layer 13. Thecoating solution may be obtained, for example, by diluting anaddition-type organopolysiloxane and a platinum catalyst and if desiredan organopolysiloxane that contains a trifunctional or tetrafunctionalsiloxane unit, to about 10-60 mass % using a solvent such as methylethyl ketone, toluene, ethyl acetate, and xylene. The heatingtemperature may preferably be about 90-180° C. and the heating time maypreferably be about 1-5 minutes

Another method of manufacturing the pressure sensitive adhesive sheet 1Aaccording to the present embodiment may include forming the inorganicfiller-containing resin layer 12 and the pressure sensitive adhesivelayer 13 in this order on the base material 11. Another method ofmanufacturing the pressure sensitive adhesive sheet 1B according to thepresent embodiment may include forming the inorganic filler-containingresin layer 12 and the pressure sensitive adhesive layer 13 onrespective surfaces of the base material 11. Another method ofmanufacturing the pressure sensitive adhesive sheet 1C according to thepresent embodiment may include forming the inorganic filler-containingresin layers 12 on both surfaces of the base material 11 and thenlaminating the pressure sensitive adhesive layer 13 on one of theinorganic filler-containing resin layers 12.

<Method of Using Pressure Sensitive Adhesive Sheet>

The pressure sensitive adhesive sheet 1A, 1B, 1C according to thepresent embodiment can be preferably used for an electronic component.Examples of the electronic component include a flexible printed board,battery, rigid board, and motor. In particular, the pressure sensitiveadhesive sheet 1A, 1B, 1C can be used in an electronic component in astate of being in contact with a conductor through which a currentflows. In this case, the surface at the pressure sensitive adhesivelayer 13 side of the pressure sensitive adhesive sheet 1A, 1B, 1C may beattached to the conductor, or the surface at the base material 11 sidemay be brought into contact with the conductor. In an embodiment, bothsurfaces of the pressure sensitive adhesive sheet 1A, 1B, 1C may bebrought into contact with conductors. The pressure sensitive adhesivesheet 1A, 1B, 1C can be used, for example, for the purpose of protectinga conductor such as an electric circuit in an electronic component. Thepressure sensitive adhesive sheet 1A, 1B, 1C can also be used for thepurpose of fixing a conductor such as an electrode in an electroniccomponent.

The pressure sensitive adhesive sheet LA, 1B, 1C according to thepresent embodiment is provided with the base material 11 havinginsulation properties and thereby has good insulation properties at anordinary time. Moreover, even when the matrices in the base material 11and/or the inorganic filler-containing resin layer 12 undergocarbonization and/or combustion/decomposition due to high temperatures,the insulation properties of the pressure sensitive adhesive sheet 1A,1B, 1C itself are ensured because the inorganic filler in the inorganicfiller-containing resin layer 12 remains as an insulating film.Furthermore, even when a high voltage is partially applied to thepressure sensitive adhesive sheet 1A, 1B, 1C to flow a current throughthe pressure sensitive adhesive sheet 1A, 1B, 1C in the thicknessdirection so that the path of the current in the base material 11changes to a conductor and the matrix in the inorganic filler-containingresin layer 12 undergoes carbonization and the like along the path ofthe current, the insulation properties of the pressure sensitiveadhesive sheet 1A, 1B, 1C itself are ensured because the inorganicfiller exists as an insulating body in the path. Owing to thesefeatures, the occurrence of short circuit and/or thermal runaway issuppressed in an electronic component for which the pressure sensitiveadhesive sheet 1A, 1B, 1C is used.

It should be appreciated that the embodiments heretofore explained aredescribed to facilitate understanding of the present invention and arenot described to limit the present invention. It is therefore intendedthat the elements disclosed in the above embodiments include all designchanges and equivalents to fall within the technical scope of thepresent invention.

For example, in the pressure sensitive adhesive sheet 1A, 1B, 1C, therelease sheet 14 may be omitted. In an embodiment, the pressuresensitive adhesive sheet 1A, 1B, 1C may be provided with one or moreother layers between the base material 11 and the inorganicfiller-containing resin layer 12.

EXAMPLES

Hereinafter, the present invention will be described furtherspecifically with reference to examples, etc., but the scope of thepresent invention is not limited to these examples, etc.

Example 1

1. Formation of Inorganic Filler-Containing Resin Layer on Base Material

A coating liquid for inorganic filler-containing resin layer wasprepared through mixing 40 mass parts of dipentaerythritol hexaacrylate(a material of which the glass-transition point is not observed aftercuring) as an active energy ray-curable component, 5 mass parts ofhydroxycyclohexyl phenyl ketone as a photopolymerization initiator, and60 mass parts (solid content equivalent, here and hereinafter) of anorganosilica sol (available from Nissan Chemical Industries, Ltd., tradename “MEK-ST,” average particle diameter of 30 nm) as an inorganicfiller and diluting them with methyl ethyl ketone. The solid contentconcentration of the coating liquid for inorganic filler-containingresin layer was 20 mass %.

One surface of a polyimide film (available from DU PONT-TORAY CO., LTD.,trade name “Kapton 100H,” thickness of 25 μm, flame retardation levelV-0 of UL94 standard) as a base material was coated with the abovecoating liquid using a knife coater and the coating liquid was thendried at 70° C. for 1 minute. Subsequently, the coating film wasirradiated with ultraviolet rays (illuminance of 230 mW/cm², lightamount of 510 mJ/cm²) to cure the coating film. A fist laminate was thusobtained in which an inorganic filler-containing resin layer having athickness of 2 μm and containing 2.0 g/m² of the inorganic filler wasformed on one surface of the base material.

2. Formation of Pressure Sensitive Adhesive Layer on Release Sheet

A (meth)acrylic ester polymer was prepared by copolymerizing 77 massparts of butyl acrylate, 20 mass parts of methyl acrylate, and 3 massparts of acrylic acid. The molecular weight of this polymer was measuredusing gel permeation chromatography (GPC), which will be describedlater. The weight-average molecular weight (Mw) was 900,000. Then, acoating liquid for pressure sensitive adhesive layer was preparedthrough mixing 100 mass parts of the (meth)acrylic ester polymer, 2.2mass parts of trimethylolpropane-modified tolylene diisocyanate(available from TOYOCHEM CO., LTD., trade name “BHS8515”) as acrosslinker, and 0.3 mass parts of aluminum tris(acetylacetonate)(available from Soken Chemical & Engineering Co., Ltd., trade name“M-5A”) as a crosslinker and diluting them with methyl ethyl ketone. Thesolid content concentration of the coating liquid for pressure sensitiveadhesive layer was 20 mass %.

A release sheet (available from LINTEC Corporation, trade name“PET251130”) was prepared in which one surface of a polyethyleneterephthalate film was subjected to release treatment using asilicone-based release agent. The release-treated surface of the releasesheet was coated with the obtained coating liquid using a knife coaterand the coating liquid was then heat-treated at 120° C. for 1 minute. Asecond laminate was thus obtained in which a pressure sensitive adhesivelayer composed of the acrylic-based pressure sensitive adhesive andhaving a thickness of 5 μm was laminated on the release-treated surfaceof the release sheet.

3. Production of Pressure Sensitive Adhesive Sheet

The surface at the inorganic filler-containing resin layer side of thefirst laminate produced as the above and the surface at the pressuresensitive adhesive layer side of the second laminate produced as theabove were attached to each other, and a pressure sensitive adhesivesheet was thus obtained.

Example 2

A coating liquid for inorganic filler-containing resin layer wasprepared through mixing 45 mass parts of a polyamideimide resin(available from “TOYOBO CO., LTD., trade name “VYLOMAX CHX02”) and 60mass parts of an organosilica sol (available from Nissan ChemicalIndustries, Ltd., trade name “MEK-ST”) as an inorganic filler anddiluting them with methyl ethyl ketone. The solid content concentrationof the coating liquid for inorganic filler-containing resin layer was 20mass %. A pressure sensitive adhesive sheet was manufactured in the samemanner as in Example 1 except that the coating liquid for inorganicfiller-containing resin layer was used. In this pressure sensitiveadhesive sheet, the content of the inorganic filler in the inorganicfiller-containing resin layer was 1.2 g/m².

Example 3

A coating liquid for pressure sensitive adhesive layer was preparedthrough mixing 100 mass parts of a silicone-based pressure sensitiveadhesive (available from Dow Corning Toray Co., Ltd., trade name“SD-4584”) and 0.5 mass parts of a catalyst (available from Dow CorningToray Co., Ltd., trade name “CAT-SRX-212”) and diluting them with methylethyl ketone. The solid content concentration of the coating liquid forpressure sensitive adhesive layer was 20 mass %. A pressure sensitiveadhesive sheet was manufactured in the same manner as in Example 1except that the coating liquid for pressure sensitive adhesive layer anda release sheet (available from LINTEC Corporation, trade name“PET50FD”) obtained by release-treating one surface of a polyethyleneterephthalate film using a fluorine-based release agent were used.

Example 4

A coating liquid for pressure sensitive adhesive layer was preparedthrough mixing 100 mass parts of polyisobutylene (available from JAPANBUTYL Co. Ltd., trade name “Exxon Butyl 268”), 5 mass parts of amethacryloyl group-containing polyisoprene rubber (available fromKURARAY CO., LTD., trade name “UC-203”), and 20 mass parts of analiphatic-based petroleum resin (available from Zeon Corporation, tradename “Quintone A100”) and diluting them with toluene. The solid contentconcentration of the coating liquid for pressure sensitive adhesivelayer was 20 mass %. A pressure sensitive adhesive sheet wasmanufactured in the same manner as in Example 1 except that the coatingliquid for pressure sensitive adhesive layer was used.

Example 5

A coating liquid for inorganic filler-containing resin layer wasprepared through mixing 40 mass parts of dipentaerythritol hexaacrylateas an active energy ray-curable component, 5 mass parts ofhydroxycyclohexyl phenyl ketone as a photopolymerization initiator, and60 mass parts of alumina ceramic nanoparticles (available from BYK JapanKK, trade name “NANOBYK-3601”) as an inorganic filler and diluting themwith methyl ethyl ketone. The solid content concentration of the coatingliquid for inorganic filler-containing resin layer was 20 mass %. Apressure sensitive adhesive sheet was manufactured in the same manner asin Example 1 except that the coating liquid for inorganicfiller-containing resin layer was used. In this pressure sensitiveadhesive sheet, the content of the inorganic filler in the inorganicfiller-containing resin layer was 2.2 g/m².

Example 6

A (meth)acrylic ester polymer was prepared by copolymerizing 60 massparts of butyl acrylate, 20 mass parts of methyl acrylate, and 20 massparts of acrylic acid. The molecular weight of this polymer was measuredusing gel permeation chromatography (GPC), which will be describedlater. The weight-average molecular weight (Mw) was 600,000. A coatingliquid for pressure sensitive adhesive layer was prepared through mixing100 mass parts of the (meth)acrylic ester polymer and 2.2 mass parts oftrimethylolpropane-modified tolylene diisocyanate (available fromTOYOCHEM CO., LTD., trade name “BHS8515”) as a crosslinker and dilutingthem with methyl ethyl ketone. The solid content concentration of thecoating liquid for pressure sensitive adhesive layer was 20 mass %. Apressure sensitive adhesive sheet was manufactured in the same manner asin Example 1 except that the coating liquid for pressure sensitiveadhesive layer was used.

Example 7

A (meth)acrylic ester polymer was prepared by copolymerizing 99 massparts of butyl acrylate and 1 mass part of 4-hydroxybutyl(meth)acrylate. The molecular weight of this polymer was measured usinggel permeation chromatography (GPC), which will be described later. Theweight-average molecular weight (Mw) was 1,500,000. A coating liquid forpressure sensitive adhesive layer was prepared through mixing 100 massparts of the (meth)acrylic ester polymer and 2.2 mass parts oftrimethylolpropane-modified tolylene diisocyanate (available fromTOYOCHEM CO., LTD., trade name “BHS8515”) as a crosslinker and dilutingthem with methyl ethyl ketone. The solid content concentration of thecoating liquid for pressure sensitive adhesive layer was 20 mass %. Apressure sensitive adhesive sheet was manufactured in the same manner asin Example 1 except that the coating liquid for pressure sensitiveadhesive layer was used.

Example 8

A coating liquid for inorganic filler-containing resin layer wasprepared through mixing 40 mass parts of dipentaerythritol hexaacrylateas an active energy ray-curable component, 5 mass parts ofhydroxycyclohexyl phenyl ketone as a photopolymerization initiator, and60 mass parts of reactive silica (silica fine particles having acryloylgroups on the surfaces, average particle diameter of 15 nm beforesurface modification of silica fine particles) as an inorganic fillerand diluting them with methyl ethyl ketone. The solid contentconcentration of the coating liquid for inorganic filler-containingresin layer was 20 mass %. A pressure sensitive adhesive sheet wasmanufactured in the same manner as in Example 1 except that the coatingliquid for inorganic filler-containing resin layer was used. In thispressure sensitive adhesive sheet, the content of the inorganic fillerin the inorganic filler-containing resin layer was 2.0 g/m².

Example 9

A pressure sensitive adhesive sheet was manufactured in the same manneras in Example 1 except that the surface at the base material side of thefirst laminate and the surface at the pressure sensitive adhesive layerside of the second laminate were attached to each other.

Example 10

A pressure sensitive adhesive sheet was manufactured in the same manneras in Example 2 except that the surface at the base material side of thefirst laminate and the surface at the pressure sensitive adhesive layerside of the second laminate were attached to each other.

Comparative Example 1

A pressure sensitive adhesive sheet was manufactured in the same manneras in Example 1 except that a polyimide film (available from DUPONT-TORAY CO., LTD., trade name “Kapton 100H,” thickness of 25 μm) as abase material was used as substitute for the first laminate and onesurface of the base film and the surface at the pressure sensitive layerside of the second laminate were attached to each other.

<Exemplary Test 1> (Measurement of Adhesive Strength)

The adhesive strength of the pressure sensitive adhesive sheets wasmeasured in accordance with JIS Z0237: 2009 except the followingoperation.

The pressure sensitive adhesive sheet obtained in each of the examplesor the comparative example was cut into a width of 25 mm and a length of250 mm and the release sheet was then removed to obtain a test piece.The exposed pressure sensitive adhesive layer of the test piece wasattached to an aluminum plate as an adherend using a rubber roller of 2kg under an environment of 23° C. and 50% RH and they were then leftuntouched under the same environment for 20 minutes. Thereafter, thetest piece was peeled off from the above aluminum plate at a peel angleof 180° and a peel speed of 300 mm/min using a universal tensile tester(available from ORIENTEC Co., LTD., “TENSILON UTM-4-100”) and the peelstrength (N/25 mm) was thus measured. The measured value was employed asthe adhesive strength. Results are listed in Table 1.

<Exemplary Test 2> (Measurement of Insulation Breakdown Voltage)

For the base material used for manufacturing the pressure sensitiveadhesive sheet in each of the examples or the comparative example, theminimum voltage at which insulation breakdown occurred (which may bereferred to as “insulation breakdown voltage,” hereinafter) was measuredin accordance with item 17 “Insulation Strength” of JIS C2107.Specifically, first, the base material was cut into 300 mm×300 mm toobtain a test piece. Then, both surfaces of the test piece wereinterposed between electrodes of a withstand voltage tester (availablefrom Keisoku Giken Co., Ltd., trade name “AC withstand voltage tester7220”). This setting was performed such that each electrode was incontact with the middle part of the test piece. Subsequently, thecurrent was set at 10 mA and the voltage was increased at a rate of 500V/s from 0 V until the insulation breakdown occurred. In this operation,the voltage at which insulation breakdown occurred was measured andrecorded. Results are listed in Table 1.

<Exemplary Test 3> (Evaluation of Insulation Properties at OrdinaryTime)

The release film (release sheet) was removed from the pressure sensitiveadhesive sheet obtained in each of the examples or the comparativeexample and the exposed pressure sensitive adhesive layer was attachedto an aluminum plate to obtain a test piece. Then, the resistance valuebetween the surface at the pressure sensitive adhesive sheet side andthe surface at the aluminum plate side of the test piece was measuredusing a digital high tester (available from HIOKI E.E. CORPORATION,trade name “3802-50”). Through this operation, the resistance value inthe thickness direction of the pressure sensitive adhesive sheet wasmeasured.

On the basis of the measured resistance value in the thickness directionof the pressure sensitive adhesive sheet, the insulating properties ofthe pressure sensitive adhesive sheet at an ordinary time were evaluatedin accordance with the following determination criteria. Evaluationresults are listed in Table 1.

∘: The resistance value in the thickness direction of the pressuresensitive adhesive sheet was 1.0×10¹⁰Ω or more.

x: The resistance value in the thickness direction of the pressuresensitive adhesive sheet was less than 1.0×10¹⁰Ω.

<Exemplary Test 4> (Evaluation of Insulation Properties after Heating)

The release film (release sheet) was removed from the pressure sensitiveadhesive sheet obtained in each of the examples or the comparativeexample and the exposed pressure sensitive adhesive layer was attachedto an aluminum plate to obtain a test piece. The test piece was heatedunder a nitrogen atmosphere environment of 800° C. for one hour. Then,the resistance value between the surface at the pressure sensitiveadhesive sheet side and the surface at the aluminum plate side of thetest piece was measured using a digital high tester (available fromHIOKI E.E. CORPORATION, trade name “3802-50”). Through this operation,the resistance value in the thickness direction of the pressuresensitive adhesive sheet was measured.

On the basis of the measured resistance value in the thickness directionof the pressure sensitive adhesive sheet, the insulating properties ofthe pressure sensitive adhesive sheet after heating were evaluated inaccordance with the following determination criteria. Evaluation resultsare listed in Table 1.

∘: The resistance value in the thickness direction of the pressuresensitive adhesive sheet was 1.0×10¹⁰Ω or more.

x: The resistance value in the thickness direction of the pressuresensitive adhesive sheet was less than 1.0×10¹⁰Ω.

<Exemplary Test 5> (Evaluation of Insulation Properties after InsulationBreakdown)

The release film (release sheet) was removed from the pressure sensitiveadhesive sheet obtained in each of the examples or the comparativeexample and the exposed pressure sensitive adhesive layer was attachedto an aluminum plate to obtain a test piece. A voltage of 10 kV wasapplied to the test piece. Then, the resistance value between thesurface at the pressure sensitive adhesive sheet side and the surface atthe aluminum plate side of the test piece was measured using a digitalhigh tester (available from HIOKI E.E. CORPORATION, trade name“3802-50”). Through this operation, the resistance value in thethickness direction of the pressure sensitive adhesive sheet wasmeasured.

On the basis of the measured resistance value in the thickness directionof the pressure sensitive adhesive sheet, the insulating properties ofthe pressure sensitive adhesive sheet after insulation breakdown wereevaluated in accordance with the following determination criteria.Evaluation results are listed in Table 1.

∘: The resistance value in the thickness direction of the pressuresensitive adhesive sheet was 1.0×10¹⁰Ω or more.

x: The resistance value in the thickness direction of the pressuresensitive adhesive sheet was less than 1.0×10¹⁰Ω.

<Exemplary Test 6> (Measurement of Gel Fraction)

In the manufacturing of the pressure sensitive adhesive sheet of each ofthe examples and comparative example, the surface at the pressuresensitive adhesive layer side of the second laminate was attached to therelease-treated surface of another release sheet (available from LINTECCorporation, trade name “PET251130”) in which one surface of apolyethylene terephthalate film was subjected to release treatment usinga silicone-based release agent. A sheet for measurement was thusobtained comprising the pressure sensitive adhesive layer alone, ofwhich both surfaces were protected by the release sheets.

The obtained sheet for measurement was cut into a size of 80 mm×80 mmand the release sheets protecting both surfaces of the pressuresensitive adhesive layer were removed. The pressure sensitive adhesivelayer was wrapped with a polyester mesh (mesh size of 200) and the totalmass was weighed using a precision balance. The mass of the pressuresensitive adhesive alone was calculated by subtracting the mass of theabove mesh alone from the total mass. The calculated mass is representedby M1. Then, the pressure sensitive adhesive wrapped with the abovepolyester mesh was immersed in ethyl acetate at 25° C. for 24 hours.Thereafter, the pressure sensitive adhesive was taken out, air-dried for24 hours under an environment of a temperature of 23° C. and a relativehumidity of 50%, and further dried in an oven at 80° C. for 12 hours.After drying, the mass was weighed using a precision balance and themass of the pressure sensitive adhesive alone was calculated bysubtracting the mass of the above mesh alone. The calculated mass isrepresented by M2. The gel fraction (%) was calculated from thecalculation formula of (M2/M1)×100. Results are listed in Table 1.

<Exemplary Test 7> (Measurement of Storage Elastic Modulus>

The release sheet was removed from the second laminate obtained in eachof the examples or the comparative example to expose the pressuresensitive adhesive layer. A plurality of such pressure sensitiveadhesive layers was laminated so as to have a thickness of 0.6 mm. Acylindrical body having a diameter of 8 mm (height of 0.6 mm) waspunched out from the obtained laminate of the pressure sensitiveadhesive layers and this was employed as a sample.

The storage elastic modulus (MPa) of the above sample was measured by atorsional shear testing method under the following condition inaccordance with JIS K7244-6 using a viscoelasticity measuring apparatus(available from Physica, MCR300). Measurement results are listed inTable 1.

Measurement frequency: 1 Hz

Measurement temperature: 120° C.

<Exemplary Test 8> (Evaluation of Pencil Hardness)

For the inorganic filler-containing resin layer of the first laminateobtained when manufacturing the pressure sensitive adhesive sheet ofeach of the examples and comparative example, the pencil hardness wasmeasured in accordance with JIS K5600-5-4. A pencil scratch hardnesstester (available from YASUDA SEIKI SEISAKUSHO, LTD., trade name “No.553-M”) was used for the measurement and the scratch speed was 1 mm/sec.Results are listed in Table 1.

TABLE 1 Example Comparative Example 1 Example 2 Example 3 Example 4Example 5 Example 6 Example 7 Example 8 Example 9 10 Example 1 Adhesive 5  5 10  6  5  7  4  5  5  6  5 strength (N/25 mm) Insulation  9  9 10 9  9  9  9  9  9  9  7 breakdown voltage (kV) Evaluation of ◯ ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ insulation properties at ordinary time Evaluation of ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ X insulation properties after heating Evaluation of ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ X insulation properties after insulation breakdown Gelfraction 80 80 90 100  80 75 85 80 80 80 80 (%) Storage elastic 72 72 8093 72 26 58 72 72 72 72 modulus at 120° C. (kPa) Pencil HB 2B HB HB HBHB HB H HB 2B 2B hardness of inorganic filler- containing resin layer

As apparent from Table 1, the pressure sensitive adhesive sheets of theexamples exhibit good insulation properties even after they are exposedto high temperatures and insulation breakdown is caused, which aredifferent from those of the pressure sensitive adhesive sheet of thecomparative example.

INDUSTRIAL APPLICABILITY

The pressure sensitive adhesive sheet of the present invention issuitable as a pressure sensitive adhesive sheet that is used inelectronic components.

DESCRIPTION OF REFERENCE NUMERALS

-   1A, 1B, 1C . . . Pressure sensitive adhesive sheet-   11 . . . Base material-   12 . . . Inorganic filler-containing resin layer-   13 . . . Pressure sensitive adhesive layer-   14 . . . Release sheet

The invention claimed is:
 1. A battery containing a pressure sensitiveadhesive sheet, wherein the pressure sensitive adhesive sheet comprises:a base material layer having a minimum breakdown voltage at whichinsulation breakdown occurs in the base material layer of 1 kV; aninorganic filler-containing resin layer provided at least at one side ofthe base material layer and containing an insulating inorganic filler; apressure sensitive adhesive layer provided as an outermost layer of atleast one surface of the pressure sensitive adhesive sheet; theinorganic filler-containing resin layer comprises a material obtained bycuring a composition that contains an active energy ray-curablecomponent and the inorganic filler; and a thickness of the inorganicfiller-containing resin layer is 2 μm or more and 10 μm or less.
 2. Thebattery as recited in claim 1, wherein the base material layer has flameretardancy that satisfies flame retardancy level V-0 of UL94 standard.3. The battery as recited in claim 1, wherein the inorganicfiller-containing resin layer is provided at the one side of the basematerial layer and the pressure sensitive adhesive layer is provided ata side of the inorganic filler-containing resin layer opposite the basematerial layer.
 4. The battery as recited in claim 1, wherein a contentof the inorganic filler in the inorganic filler-containing resin layeris 0.5-50 g/m².
 5. A battery containing a pressure sensitive adhesivesheet having improved breakdown voltage insulation, wherein the pressuresensitive adhesive sheet comprises: a base material layer having aminimum voltage at which insulation breakdown occurs in the basematerial layer of 1 kV; an inorganic filler-containing resin layerprovided at least at one side of the base material layer and containingan insulating inorganic filler, the inorganic filler-containing resinlayer comprising a material obtained by curing a composition thatcontains an active energy ray-curable component and the inorganicfiller, and the inorganic filler-containing resin layer having athickness of 2 μm or more and 10 μm or less; a pressure sensitiveadhesive layer provided as an outermost layer of at least one surface ofthe pressure sensitive adhesive sheet.
 6. The battery as recited inclaim 5, wherein the base material layer has flame retardancy thatsatisfies flame retardancy level V-0 of UL94 standard.
 7. The battery asrecited in claim 5, wherein the inorganic filler-containing resin layeris provided at the one side of the base material layer and the pressuresensitive adhesive layer is provided at a side of the inorganicfiller-containing resin layer opposite the base material layer.
 8. Thebattery as recited in claim 5, wherein a content of the inorganic fillerin the inorganic filler-containing resin layer is 0.5-50 g/m².
 9. Thebattery as recited in claim 1, wherein the active energy ray-curablecomponent of the inorganic filler-resin containing layer has aglass-transition point after curing of 130° C. or higher.
 10. Thebattery as recited in claim 1, wherein the pressure sensitive adhesivesheet originally has a resistance in its thickness direction of 1.0×10¹⁰ohms or more and maintains the resistance of 1.0×10¹⁰ ohms or more afterbeing heated to 800° C. in a nitrogen atmosphere for one hour.
 11. Thebattery as recited in claim 5, wherein the pressure sensitive adhesivesheet originally has a resistance in its thickness direction of 1.0×10¹⁰ohms or more and maintains the resistance of 1.0×10¹⁰ ohms or more afterbeing heated to 800° C. in a nitrogen atmosphere for one hour.
 12. Abattery containing a pressure sensitive adhesive sheet in contact withan electrical conductor, the pressure sensitive adhesive sheet having aresistance in its thickness direction of 1.0×10¹⁰ ohms or more, and thepressure sensitive adhesive sheet comprising: a base material layerhaving a minimum breakdown voltage at which insulation breakdown occursin the base material layer of 1 kV; an inorganic filler-containing resinlayer provided at least at one side of the base material layer andcontaining an insulating inorganic filler; a pressure sensitive adhesivelayer provided as an outermost layer of at least one surface of thepressure sensitive adhesive sheet; the inorganic filler-containing resinlayer comprises a material obtained by curing a composition thatcontains an active energy ray-curable component and the inorganicfiller; and a thickness of the inorganic filler-containing resin layeris 2 μm or more and 10 μm or less, wherein the pressure sensitiveadhesive sheet maintains the resistance of 1.0×10¹⁰ ohms or more afterbeing heated to 800° C. in a nitrogen atmosphere for one hour.
 13. Thebattery as recited in claim 12, wherein the base material layer hasflame retardancy that satisfies flame retardancy level V-0 of UL94standard.
 14. The battery as recited in claim 12, wherein the inorganicfiller-containing resin layer is provided at the one side of the basematerial layer and the pressure sensitive adhesive layer is provided ata side of the inorganic filler-containing resin layer opposite to thebase material layer.
 15. The battery as recited in claim 12, wherein acontent of the inorganic filler in the inorganic filler-containing resinlayer is 0.5-50 g/m².
 16. The battery as recited in claim 12, wherein asurface of the pressure sensitive adhesive layer side of the pressuresensitive adhesive sheet is attached to the conductor.
 17. The batteryas recited in claim 12, wherein a surface of the pressure sensitiveadhesive sheet on a side opposite the pressure sensitive adhesivecontacts the electrical conductor.
 18. The battery as recited in claim12, wherein the active energy ray-curable component of the inorganicfiller-resin containing layer has a glass-transition point after curingof 130° C. or higher.